Bio 101 Krebs Cycle Steps
38 flashcards covering Bio 101 Krebs Cycle Steps for the BIOLOGY-101 Energy & Metabolism section.
The Krebs Cycle, also known as the citric acid cycle, is a crucial metabolic pathway that plays a central role in cellular respiration. It is defined in the curriculum for Introductory Biology I courses and is essential for understanding how cells convert nutrients into energy. This cycle involves a series of enzymatic reactions that produce ATP, NADH, and FADH2, which are vital for energy transfer in biological systems.
On practice exams and competency assessments, questions about the Krebs Cycle often focus on the sequence of steps, the enzymes involved, and the products generated. Common question formats include multiple-choice and fill-in-the-blank, where candidates may be asked to identify specific intermediates or enzymes. A frequent pitfall is confusing the cycle's steps with those of glycolysis, leading to incorrect answers about energy yield and metabolic connections.
One important tip is to memorize the cycle's intermediates in order, as this will help prevent mix-ups during assessments.
Terms (38)
- 01
What is the first step of the Krebs cycle?
The first step of the Krebs cycle is the condensation of acetyl-CoA with oxaloacetate to form citrate, catalyzed by the enzyme citrate synthase (Campbell Biology, chapter on cellular respiration).
- 02
What molecule is regenerated at the end of the Krebs cycle?
At the end of the Krebs cycle, oxaloacetate is regenerated, allowing the cycle to continue (Campbell Biology, chapter on cellular respiration).
- 03
How many NADH molecules are produced in one turn of the Krebs cycle?
One turn of the Krebs cycle produces three NADH molecules (Campbell Biology, chapter on cellular respiration).
- 04
What is the role of FAD in the Krebs cycle?
FAD acts as an electron carrier, being reduced to FADH2 during the conversion of succinate to fumarate in the Krebs cycle (Campbell Biology, chapter on cellular respiration).
- 05
Which enzyme catalyzes the conversion of citrate to isocitrate?
The enzyme aconitase catalyzes the conversion of citrate to isocitrate in the Krebs cycle (Campbell Biology, chapter on cellular respiration).
- 06
What is produced during the decarboxylation steps of the Krebs cycle?
During the decarboxylation steps of the Krebs cycle, carbon dioxide (CO2) is produced (Campbell Biology, chapter on cellular respiration).
- 07
How many ATP are generated directly from one turn of the Krebs cycle?
One turn of the Krebs cycle generates one ATP (or GTP) through substrate-level phosphorylation (Campbell Biology, chapter on cellular respiration).
- 08
What is the significance of the Krebs cycle in cellular respiration?
The Krebs cycle is crucial for generating electron carriers (NADH and FADH2) that feed into the electron transport chain, ultimately leading to ATP production (Campbell Biology, chapter on cellular respiration).
- 09
Which step of the Krebs cycle involves the conversion of malate to oxaloacetate?
The conversion of malate to oxaloacetate is catalyzed by the enzyme malate dehydrogenase (Campbell Biology, chapter on cellular respiration).
- 10
What are the main products of one complete turn of the Krebs cycle?
One complete turn of the Krebs cycle produces 3 NADH, 1 FADH2, 1 ATP (or GTP), and 2 CO2 (Campbell Biology, chapter on cellular respiration).
- 11
How does acetyl-CoA enter the Krebs cycle?
Acetyl-CoA enters the Krebs cycle by combining with oxaloacetate to form citrate, which initiates the cycle (Campbell Biology, chapter on cellular respiration).
- 12
What is the function of the enzyme succinate dehydrogenase in the Krebs cycle?
Succinate dehydrogenase catalyzes the oxidation of succinate to fumarate, producing FADH2 in the process (Campbell Biology, chapter on cellular respiration).
- 13
Which compound is formed when citrate is converted to isocitrate?
The compound formed when citrate is converted to isocitrate is cis-aconitate, as an intermediate (Campbell Biology, chapter on cellular respiration).
- 14
What happens to the carbon atoms in acetyl-CoA during the Krebs cycle?
The carbon atoms in acetyl-CoA are released as carbon dioxide (CO2) during the decarboxylation reactions of the Krebs cycle (Campbell Biology, chapter on cellular respiration).
- 15
What is the role of water in the Krebs cycle?
Water is involved in the hydration reactions, such as the conversion of fumarate to malate (Campbell Biology, chapter on cellular respiration).
- 16
Which enzyme catalyzes the conversion of isocitrate to alpha-ketoglutarate?
The enzyme isocitrate dehydrogenase catalyzes the conversion of isocitrate to alpha-ketoglutarate (Campbell Biology, chapter on cellular respiration).
- 17
What is the energy yield from NADH produced in the Krebs cycle?
Each NADH produced in the Krebs cycle can yield approximately 2.5 ATP when oxidized in the electron transport chain (Campbell Biology, chapter on cellular respiration).
- 18
How many times does the Krebs cycle turn per glucose molecule?
The Krebs cycle turns twice per glucose molecule, as each glucose yields two acetyl-CoA molecules (Campbell Biology, chapter on cellular respiration).
- 19
What is the significance of the Krebs cycle intermediates?
Krebs cycle intermediates serve as precursors for various biosynthetic pathways, contributing to the synthesis of amino acids and other biomolecules (Campbell Biology, chapter on cellular respiration).
- 20
What is produced during the conversion of alpha-ketoglutarate to succinyl-CoA?
During the conversion of alpha-ketoglutarate to succinyl-CoA, one molecule of NADH and one molecule of CO2 are produced (Campbell Biology, chapter on cellular respiration).
- 21
Which step of the Krebs cycle involves substrate-level phosphorylation?
Substrate-level phosphorylation occurs when succinyl-CoA is converted to succinate, producing ATP (or GTP) (Campbell Biology, chapter on cellular respiration).
- 22
What is the role of Coenzyme A in the Krebs cycle?
Coenzyme A is involved in the formation of acetyl-CoA, which enters the Krebs cycle (Campbell Biology, chapter on cellular respiration).
- 23
How does the Krebs cycle contribute to aerobic respiration?
The Krebs cycle contributes to aerobic respiration by generating electron carriers that drive ATP production through oxidative phosphorylation (Campbell Biology, chapter on cellular respiration).
- 24
What is the final product of the Krebs cycle?
The final product of the Krebs cycle is oxaloacetate, which is regenerated to continue the cycle (Campbell Biology, chapter on cellular respiration).
- 25
Which enzyme catalyzes the conversion of fumarate to malate?
The enzyme fumarase catalyzes the conversion of fumarate to malate in the Krebs cycle (Campbell Biology, chapter on cellular respiration).
- 26
What is the function of the Krebs cycle in metabolism?
The Krebs cycle functions to oxidize acetyl-CoA, producing energy-rich electron carriers and carbon dioxide as waste (Campbell Biology, chapter on cellular respiration).
- 27
What is the role of NAD+ in the Krebs cycle?
NAD+ serves as an electron acceptor, being reduced to NADH during the oxidation of substrates in the Krebs cycle (Campbell Biology, chapter on cellular respiration).
- 28
What is the importance of the Krebs cycle in cellular respiration?
The Krebs cycle is essential for the complete oxidation of carbohydrates, fats, and proteins, contributing to the overall energy yield of cellular respiration (Campbell Biology, chapter on cellular respiration).
- 29
How many CO2 molecules are released in one turn of the Krebs cycle?
One turn of the Krebs cycle releases two CO2 molecules during the decarboxylation reactions (Campbell Biology, chapter on cellular respiration).
- 30
What is the main purpose of the Krebs cycle?
The main purpose of the Krebs cycle is to generate high-energy electron carriers (NADH and FADH2) for the electron transport chain (Campbell Biology, chapter on cellular respiration).
- 31
Which step of the Krebs cycle involves the conversion of succinate to fumarate?
The conversion of succinate to fumarate is catalyzed by the enzyme succinate dehydrogenase (Campbell Biology, chapter on cellular respiration).
- 32
What is the role of citrate in the Krebs cycle?
Citrate is the first product formed in the Krebs cycle and serves as a substrate for subsequent reactions (Campbell Biology, chapter on cellular respiration).
- 33
What is the significance of GTP in the Krebs cycle?
GTP produced during the Krebs cycle can be readily converted to ATP, providing energy for cellular processes (Campbell Biology, chapter on cellular respiration).
- 34
How does the Krebs cycle connect to the electron transport chain?
The NADH and FADH2 produced in the Krebs cycle donate electrons to the electron transport chain, facilitating ATP production (Campbell Biology, chapter on cellular respiration).
- 35
What is the relationship between the Krebs cycle and fatty acid metabolism?
The Krebs cycle is linked to fatty acid metabolism through the conversion of fatty acids into acetyl-CoA, which enters the cycle (Campbell Biology, chapter on cellular respiration).
- 36
What is the role of oxaloacetate in the Krebs cycle?
Oxaloacetate acts as a reactant that combines with acetyl-CoA to initiate the Krebs cycle (Campbell Biology, chapter on cellular respiration).
- 37
Which enzyme is responsible for the conversion of malate to oxaloacetate?
Malate dehydrogenase is responsible for the conversion of malate to oxaloacetate in the Krebs cycle (Campbell Biology, chapter on cellular respiration).
- 38
What is the effect of inhibiting the Krebs cycle?
Inhibiting the Krebs cycle can lead to reduced ATP production and accumulation of metabolic intermediates, affecting cellular respiration (Campbell Biology, chapter on cellular respiration).